A lithium mixed metal oxide is used as a positive electrode active material for a nonaqueous electrolyte secondary battery such as a lithium secondary battery. The lithium secondary battery has already been in practical use as a power source for a cell phone, a notebook-size personal computer, or the like, and furthermore its application has been tried also in medium- to large-sized uses such as automobile use and power storage use.
As the conventional lithium mixed metal oxide, Li(Mn0.1Ni0.45Fe0.45)O2 is concretely disclosed in Patent Document 1.